Mobile communication networks typically comprise many network nodes, e.g. radio base stations, that are used to provide coverage to wireless devices, also known as instances of user equipment (UEs). However, the wireless devices experience interference from neighbouring network nodes, particularly in border areas between cells. Such interference limits the link quality for the wireless devices, resulting in limited spectral efficiency and throughput.
Coordinated multi-point reception (CoMP) is one way to attempt to increase uplink throughput by increasing the received signal power and by suppressing interference.
Moreover, radio base stations are often equipped with several receive antennas. The radio signal from a wireless device can be received by combining signals from these several antennas to increase the received signal power and receive diversity. Combining signals from several antennas also makes it possible to suppress interference by Interference Rejection Combining (IRC).
Although IRC is optimum when the propagation channel and noise plus interference covariance matrix are known in the receiver, estimation errors of the channel and of the noise plus interference covariance matrix may degrade the performance of IRC so that its performance is worse than that of maximum ratio combining (MRC).
IRC between antennas in a single sector is in the following referred to as intra-sector IRC. IRC between antennas in more than one sector is denoted inter-sector IRC.
In many deployments, antenna signals used for combining are located in the same sector, also referred to as single-point reception. In order to further increase the received signal power and to further suppress interference, antenna signals from different sectors several reception points may be combined, known as multi-point reception. Antenna signals may also be sent from one base station to another to be used for combining in the latter base station. Multi-point reception is also known as macro diversity, in Universal Terrestrial Radio Access more specifically as soft handover or softer handover.
IRC and MRC are candidates for combining both in single-point reception and multi-point reception.
U.S. Pat. No. 6,128,355 presents a method and system for combining signals in a receiver employing antenna diversity. If the interference exceeds a predetermined threshold, interference rejection combining (IRC) is used. If the interference does not exceed the predetermined threshold, maximum ratio combining (MRC) is used.
However, in multi-point reception the interference level may be different in different sectors. Furthermore, the interference may either be correlated or uncorrelated between sectors. IRC and MRC provide too few alternatives to successfully adapt to different interference scenarios for multi-point reception.